Investigation of the Effect of Alloying Elements and Water Vapor Contents on the Oxidation and Decarburization of Transformation-Induced Plasticity Steels

Abstract

The present research deals with an investigation of the effect of alloying element additions (Si, P, and Sb) and water vapor content $\left( {{{{\text{P}}_{{{\text{H}}_{ 2} {\text{O}}}} } \mathord{\left/ {\vphantom {{{\text{P}}_{{{\text{H}}_{ 2} {\text{O}}}} } {{\text{P}}_{{{\text{H}}_{ 2} }} }}} \right. \kern-\nulldelimiterspace} {{\text{P}}_{{{\text{H}}_{ 2} }} }} = 0.01{\text{ to }}0.13} \right)$ on the oxidation and decarburization behavior of transformation-induced plasticity (TRIP) steels in a gas mixture of 95 vol pct argon and 5 vol pct hydrogen/steam, by thermogravimetry (TG). The oxidation proceeds primarily as an internal oxidation front in the TRIP steels, but a thin external scale on the order of a micrometer thickness exists and is comprised primarily of fayalite ((Mn,Fe)₂SiO₄) and ((MnO) _x (FeO)_1−x . The oxidation products are distributed near the surface and along grain boundaries. A comparison between calculated and measured oxidation curves indicated that the oxidation and decarburization are independent. The results for TRIP steels, both with and without an Sb addition, indicate that increasing Si and P contents accelerate, whereas Sb addition suppresses, both decarburization and oxidation rates. Water vapor content has no obvious effect on decarburization but has a pronounced effect on oxidation, and decreasing water vapor content decreases the oxidation rates.